feat: vfs - add stat syscall

kernel/src/Fs/Vfs.hpp

@@ -18,6 +18,17 @@ namespace Fs::Vfs {
         uint32_t generation;
     };
 
+    // Metadata for a single path, filled by FsDriver::Stat. Timestamps are UTC
+    // unix seconds; a filesystem that does not record a given time leaves it 0.
+    struct StatInfo {
+        uint64_t size;    // file size in bytes
+        int64_t  mtime;   // last data modification time
+        int64_t  ctime;   // last inode (metadata) change time
+        int64_t  atime;   // last access time
+        uint32_t mode;    // ext2/POSIX i_mode bits (type + permissions)
+        bool     isDir;   // true if the entry is a directory
+    };
+
     struct FsDriver {
         int (*Open)(const char* path);
         int (*Read)(int handle, uint8_t* buffer, uint64_t offset, uint64_t size);
@@ -33,6 +44,9 @@ namespace Fs::Vfs {
         // Optional: paginated directory read returning entries [startIndex, startIndex+maxEntries).
         // Drivers that leave this null are read via ReadDir at startIndex 0 only.
         int (*ReadDirAt)(const char* path, const char** outNames, int maxEntries, int startIndex);
+        // Optional: fill metadata for a path. Drivers that leave this null do
+        // not support stat and VfsStat returns -1 for their paths.
+        int (*Stat)(const char* path, StatInfo* out);
     };
 
     void Initialize();
@@ -51,6 +65,7 @@ namespace Fs::Vfs {
     void CloseBackendFile(BackendFile& file);
 
     int VfsDelete(const char* path);
+    int VfsStat(const char* path, StatInfo& out);
     int VfsReadDir(const char* path, const char** outNames, int maxEntries);
     int VfsReadDirAt(const char* path, const char** outNames, int maxEntries, int startIndex);
     int VfsMkdir(const char* path);